In the field of oil and gas well exploration and exploitation, perforation is a key link in the completion of a well, and the degree of perfection of the perforation decides the productivity and lifespan of an oil and gas well. Shaped charge perforation is the common technique currently applied in perforation for oil and gas wells. Using simple shape charged perforation, a compaction zone of certain thickness is formed in the wall of the bore which leads to a drastic decrease in its permeability and severely impacts the productivity and lifespan of the oil and gas wells. To overcome this problem, the combined perforation technique was developed.
Combined perforation uses a combination of shape charged perforation and gunpowder. Upon the completion of perforation, gunpowder was used to deflagrate the gases generated at the stratum so as to remove any clogging contaminants, eradicate the compaction zone in the bore and achieve the aim of increasing both injection and productivity of the oil and gas wells. At present, most of the gunpowder is placed in guns for combined perforations in oil fields due to the simplicity of its construction, safety, reliability and little damage to the well bore. However, as the gunpowder had to be placed in shells in these combined perforator, the amount of gunpowder had to be drastically decreased, especially when space is limited at high hole density. This has led to poor results.